1. Field of the Invention
The present invention relates to a method and an apparatus for cooling a steel strip in a continuous annealing line.
2. Description of the Prior Art
In recent years, various efforts have been made to increase productivity and save man power by providing a temper rolling mill within a continuous annealing line. These efforts have, however, met with difficulties since a long period of time is required for cooling the steel strip after the overageing treatment to a temperature (about 40.degree. C.) at which the tempering treatment can be carried out and this in turn means that the annealing line must be made excessively long.
In order to overcome this problem, attempts have been made to forcedly cool the steel strip by blowing a low-temperature gas thereon but these efforts have not resulted in as great a shortening of the annealing line as had been hoped for.
On the other hand, it has been proposed to cool the strip from the overageing temperature to temperatures below 80.degree. C. to 100.degree. C. by first cooling the strip in the furnace and then water cooling the strip to a temperature at which temper rolling can be carried out. This method also has the disadvantage that a considerably long period of time is required for cooling from the overageing temperature to below 80.degree. C. to 100.degree. C.